VEIN. 



and tranfition rocks, except trap and ferpentine, in the 

 lower fecondary ftrata, and in porphyry and fienite. See 

 Lead and Zinc. 



Antimony occurs in veins in primary and tranfition moun- 

 tains, except trap and ferpentine. 



Bifmuth, cobalt, and nickel, occur in primary and tranfi- 

 tion mountains, except lime-ftone, trap, and ferpentine. 

 Cobalt and nickel alfo occur in tranfition mountains, and in 

 fand-ftone. See Bismuth, &c. 



Arfenic occurs in veins, either as a fulphuret or mi- 

 neralizer of other metals, in primary and tranfition moun- 

 tains, and in porphyry. See Arsenic. 



Tellurium occurs in veins in porphyry, combined with 

 gold. See Tellurium Mines. 



Manganefe occurs in beds and veins in primary and tranfi- 

 tion mountains, and in beds, and difleminated in red fand- 

 ilone. See Manganese. 



Molybdena, tungften, and titanium, occur in granite, 

 gneifs, mica-flate, and argillaceous fchiftus. Thefe metals, 

 with chromium and cerium, are very rare, and can only be 

 reduced to the metallic flate with great difficulty. See 

 Molybdena, &c. 



Mineral veins differ from metallic veins, being deftitute 

 of ores, and filled with the fame fubftances which compofe 

 entire rocks, or with earthy minerals. 



Quartz veins (fee Quartz) refemble in their ftrufture 

 and pofition many metallic veins ; and it not unfrequently 

 happens that a vein, which contains metallic ore in one part, 

 intermixed with quartz and other vein-ftones, will, in an- 

 other part, be entirely filled with quartz. Quartz veins 

 interfeft almoft all primary and tranfition rocks, but are 

 particularly abundant in rocks of argillaceous fchiftus and 

 greywacke. (See Rock.) The quartz in veins is moft 

 frequently white, and nearly opaque ; and being much 

 harder than the rocks which it interfeits, it remains on the 

 fummits of mountains, after the furface of the rock is de- 

 compofed, until it is carried down by diluvial currents into 

 the beds of rivers, where it becomes rounded by attrition, 

 and is tranfported to diftant diftrifts. Moft of the white 

 quartz pebbles in England have probably been formed from 

 the quartz veins of decompofed rocks, as no quartz of a 

 ftmilar kind exifts as a rock in any part of England or 

 Wales ; but the fame mineral abounds in veins. 



Granite, argillaceous fchift or flate, porphyry, green- 

 Hone, pitch-ftone, bafalt, and various other rocks, fre- 

 quently fotm veins in mountains of the fame kind with 

 themfelves, or in different rocks. Where a vein of one kind 

 of rock interfefts a rock of a fimilar kind, the fubftance of 

 the vein generally differs from that of the rock in texture, 

 colour, and other charafters. The granite in veins, which 

 paifes through granitic rocks, will generally be coarfer or 

 iiner grained than the rock which it pafTes through, and 

 have the conftituent parts differently mixed. The followers 

 of Werner alfert, that veins which contain rock fubftances 

 have been filled from above by matter poured into the fif- 

 fures, and that the granite in veins is of a fecondary form- 

 ation. They further maintain, that the lower rocks, which 

 they confider as the older, never rife into the upper rocks in 

 the form of veins. In oppofition to this opinion, it has 

 been difcovered that veins of granite, in Cornwall, may be 

 diftinftly feen rifing into the fchift or killas which covers the 

 granite rocks in many parts of that county, particularly at 

 St. Michael's mount, eaft of Penzance, and at Moufehole, 

 two miles weft of that town. Where the junftion of the 

 granite and fchift is expofed by the aftion of the fea, veins 

 oi the former rock may be traced, at low wat?r, running 

 in a zigzag form for many yards into fchift, gradually 



growing narrower, and terminating in fmall branches and 

 firings. One circumftance we obferved in thefe granite 

 veins at Moufehole, which may deferve notice : the fame vein 

 which penetrated the fchift, when it entered the granite, 

 was different in texture from the granite rock, though it 

 had the fame conftituent parts ; it might be diftinftly traced 

 for a confiderable diftance into the granite. The granite 

 alfo, in the vicinity of the fchift, was fmaller grained than 

 the general body of the rock ; and the fchift, where in 

 junftion with the granite rock or granite veins, was changed 

 to a kind of very fine-grained gneifs. Thefe fafts feem to 

 indicate that both the granite and the fchift, to a confider- 

 able diftance from their junftion, had been in a foftened 

 ftate at the fame time, and that their confolidation was con- 

 temporaneous. Similar appearances, with an intermixture 

 of veins of fchift in granite, are prefented at Glentilt, and 

 other parts of Scotland. Veins of granite, porphyry, or 

 fchift, never penetrate the upper fecondary ftrata ; but veins 

 of bafalt and trap (fee Trap) have been found in every 

 kind of rock, even penetrating chalk. Thefe veins are 

 fometimes of vaft extent and width, and frequently occafion 

 great diflocations and derangements in the ftratified rocks, 

 particularly in the coal ftrata, where they have been moft 

 obferved : hence they are called faults. ( See Fault and 

 Strata.) The diflocation of the ftrata by a vein of this 

 kind is reprefented in Plate II. Geology, Jig. 8, where the 

 different ftrata, c, d, e, f, g, on the left-hand fide, are fepa- 

 rated from the correfponding ftrata on the right, and con- 

 fiderably elevated. 



As the veins of trap or bafalt are nearly vertical, and 

 often feveral yards in width, and the fubftance with which 

 they are filled being frequently harder than the ftrata 

 which they interfeft, thefe veins remain when the furface 

 is decompofed to a confiderable depth, rifing like a wall or 

 fence, which, in the language of North Britain, is fynoni- 

 mous with dyke ; hence fuch veins have been called dykes, 

 or <whin-dykes, the term whin-ftone being ufed to denote 

 bafaltic rocks. (See Whin-stone.) Bafaltic veins, or 

 whin-dykes, vary in vcidth from a few inches to feveral 

 yards, and are fometimes more than one hundred yards wide. 

 They often extend many miles in length ; in other inftances 

 they terminate at (horter diftances, forming irregular wedge- 

 fhaped maffes. When bafaltic dykes are of confiderable 

 width, the bafalt is interfered by fiffures ; and fometimes the 

 central parts and fometimes the fides are harder or fofter 

 than the other ; and in fome parts the bafalt graduates into 

 a dark ferruginous clay. Maffes of bafalt from the dyke 

 are frequently found wedged in between the ftrata, extend- 

 ing to fome diftance : and where bafaltic dykes interfeft 

 coal ftrata, the coal in the immediate vicinity of the dyke 

 has frequently the appearance of being charred. At Cork- 

 field-fell, in the county of Durham, the coal ftrata are cut 

 through by a bafaltic vein or whin-dyke, which is about 

 feventcen yards wide. Where it comes in contaft with the 

 coal, the latter fubftance, for feveral feet, is converted into 

 a pulverulent ftate, hke foot. At a greater diftance from 

 the bafalt, the coal is reduced to a coke or cinder, which 

 burns without fmoke, and with a clear durable heat. At 

 the diftance of fifty feet from the bafalt, the coal is found 

 in the ftate of common mineral coal. The roof over the 

 coal is lined with bright cryftals of fulphur, probably fub- 

 limed by heat from the pyrites common to coal. In thefe 

 appearances we recognize every circumftance which might 

 be expefted from the agency of heat, but which would be 

 extremely difficult to reconcile with the aqueous formation 

 of bafalt. We have feen fimilar appearances near bafaltic 

 dykes in Northumberland. The vein, or dyke, of bafalt 

 4T 2 



